1. Field of the Invention
The present invention relates to techniques for retrieving information. More specifically, the present invention relates to systems and methods for performing searches for information based on spoken queries.
2. Related Art
Speech is attractive mode of input for a variety of applications. Unfortunately, user interfaces based on speech are often ineffective or unreliable due to the limitations of existing speech-recognition techniques. This is especially true in situations where the vocabulary and subject matter of interest is open-ended, such as when individuals provide arbitrary requests or queries when retrieving information or performing search tasks
A speech-recognition engine typically transforms a spoken utterance into a recognized sequence of words by matching the acoustic data and candidate word sequences, as well as the probability of occurrence of the candidate word sequences in a language model. These language models typically include statistics on the relative frequencies of words and word sequences in a subject or a domain.
Unfortunately, such language models may not be able to accommodate open-ended querying. In particular, an especially difficult problem is the so-called “out-of-vocabulary problem” in which the spoken utterance contains words that are not known to the speech-recognition engine (for example, if the words are outside of the training set or formal grammar on which the language model is based). In such cases, it is difficult if not impossible for the speech-recognition engine to recognize the intended words.
Furthermore, existing speech-recognition engines typically select a single word sequence, even if there are other alternative hypotheses that are almost as good of a match as the selected sequence. As a consequence, such approaches may not offer sufficient flexibility or potential for remedial action when errors occur. Collectively, these difficulties complicate the challenges associated with retrieving information and make it less likely that a search will return meaningful results in response to such speech queries.
Hence what is needed is a method and an apparatus that facilitates searching for information based on spoken queries without the above-described problems.